Electric tools

ABSTRACT

An electric tool may include a tubular housing, a motor disposed within the housing, and a tool holder rotatably driven by the motor and capable of holding an end tool. A shoe may be supported by the housing and may determine a protruding length of the end tool from one end of the housing. A battery mount portion may be disposed at the other end of the housing. The battery may be mounted to the battery mount portion as the battery is slid relative to the battery mount portion along a direction intersecting the extending direction of the housing.

This is a Continuation of U.S. application Ser. No. 13/960,307 filedAug. 6, 2013, now U.S. Pat. No. 9,669,534, which claims the benefit ofJapanese Application No. 2012-181191 filed Aug. 17, 2012 and JapaneseApplication No. 2012-181194 filed Aug. 17, 2012. The disclosures of theprior applications are hereby incorporated by reference herein in theirentireties.

BACKGROUND OF THE INVENTION

Field of the Invention

Embodiments of the present invention relate to electric tools to whichend tools can be mounted so as to be rotatably driven for machiningworkpieces.

Description of the Related Art

Electric rotary tools called dust-proof board trimmers or cut-out toolsare known. Such electric rotary tools may be used for various machiningoperations, such as cut-out operations for cutting plaster boards or thelike. For example, this type of electric tool is disclosed in“INSTRUCTION MANUAL DUST-PROOF BOARD TRIMMER MODEL 3706” published byMakita Corporation in February 2006. This type of electric tool mayinclude a drive motor for generating a rotational drive force and anoutput spindle (output shaft) that is rotatably driven by the rotationaldrive force of the drive motor. A mount mechanism may be disposed at thefront end of the output spindle for mounting a machining bit (end tool).A bit selected according to the machining operation, such as a cut-outoperation described above, to be performed, may be mounted to the mountmechanism. The mount mechanism may allow replacement of various bits.The replacement operation of the bit may be made by using a dedicatedtool, such as a spanner, operable to loosen and fasten the mountmechanism.

In this kind of electric rotary tool, a shoe protruding from theelectric rotary tool may be provided for determining a protrudingdistance of the bit mounted to the mount mechanism. In general, the shoemay be mounted to a housing of the electric rotary tool so as to bemovable relative thereto. In addition, a rechargeable battery may beattached to the electric rotary tool for supplying an electric power tothe drive motor. Therefore, a battery mount portion may be provided onthe electric rotary tool for mounting the battery.

There has been a need in the art for further improving this kind ofelectric tool.

SUMMARY OF THE INVENTION

In one aspect according to the present teachings, an electric tool mayinclude a tubular housing extending along a first direction, a motordisposed within the housing, and a tool holder capable of beingrotatably driven by the motor. The tool holder may hold an end tool, sothat the end tool protrudes outside from a first end of the housing. Ashoe may be supported by the housing and may be configured to determinea protruding length of the end tool held by the tool holder. A batterymount portion may be disposed at a second end opposite to the first endof the housing. The battery may be mounted to the battery mount portionas the battery is slid along a second direction relative to the batterymount portion. The second direction may intersect the first direction.

In this way, the battery may be mounted to the battery mount portion bysliding the battery along the second direction that intersects the firstdirection, along which the tubular housing extends. Therefore, forexample, in the case that the electric tool is positioned such that thetubular housing extends in the horizontal direction, the battery may bemounted to the battery mount portion by sliding the battery along thebattery mount portion in a direction intersecting the horizontaldirection. Hence, the mounting operation of the battery can be easilyperformed, and eventually, the operability of the electric tool can beimproved.

The shoe may be movable in the first direction for changing the positionrelative to the housing. Therefore, the shoe may be configured to extendin the same direction as the extending direction of the housing. Hence,it may be possible to configure the electric tool to have a relativelysmall thickness at the region of the shoe. As a result, the electrictool may be improved in its operability also in this respect.

The electric tool may further include a lock device and a shoe fixingdevice. The lock device may prevent rotation of the tool holder relativeto the housing. The shoe fixing device may fix the shoe in positionrelative to the housing. The lock device and the shoe fixing device maybe arranged at positions symmetrical with each other with respect to acentral axis of the housing. The central axis of the housing may extendalong the first direction.

With this arrangement, it is possible to reduce the size in the firstdirection of the electric tool at the region around the shaft lockmechanism and the shoe fixing device. Hence, it is possible to reducethe length of the electric tool. As a result, the electric tool may beimproved in its operability also in this respect.

The lock device and the shoe fixing device may be arranged along a thirddirection that intersects both the first direction and the seconddirection. With this arrangement, the shaft lock mechanism and the shoefixing device may be efficiently three-dimensionally arranged. Hence, itis possible to reduce the size of the electric tool at the region aroundthe shaft lock mechanism and the shoe fixing device.

In another aspect according to the present teachings, an electric toolmay include a tubular housing extending along a first direction, a motordisposed within the housing, and a tool holder capable of beingrotatably driven by the motor. The tool holder may hold an end tool, sothat the end tool protrudes outside from a first end of the housing. Ashoe may be supported by the housing and may be configured to determinea protruding length of the end tool held by the tool holder. The shoemay be movable in the first direction for changing the position relativeto the housing. The electric tool may further include a shoe fixingdevice configured to fix the shoe in position relative to the housing bya single operation.

With this arrangement, the operation for fixing the position of the shoeafter determining the position of the shoe can be performed by a singleoperation (one-touch operation). Therefore, the fixing operation of theshoe can be easily performed. The electric tool may be improved inoperability in this respect.

In a further aspect of the present teachings, an electric tool mayinclude a tubular housing extending along a first direction, a motordisposed within the housing, and a tool holder capable of beingrotatably driven by the motor. The tool holder may hold an end tool, sothat the end tool protrudes outside from a first end of the housing. Ashoe may be supported by the housing and may be configured to determinea protruding length of the end tool held by the tool holder. Theelectric tool may further include a lock device, a shoe fixing deviceand an operation input device. The lock device may prevent rotation ofthe tool holder relative to the housing. The shoe fixing device may fixthe shoe in position relative to the housing. The lock device and theshoe fixing device may be arranged at positions symmetrical with eachother with respect to a central axis of the housing. The central axis ofthe housing may extend along the first direction. The electric tool mayfurther include an operation input device configured to allow an inputoperation relating to the rotational drive of the motor. The operationinput device may be disposed at a position along a directionintersecting a direction along which the lock device and the shoe fixingdevice are arranged.

With the arrangement of the lock device and the shoe fixing device atpositions symmetrical with each other with respect to the central axisof the housing extending along the first direction, it is possible tominimize the length in the first direction of a space that may benecessary for the lock device and the shoe fixing device. Therefore, thelength of the electric tool can be minimized. The electric tool may beimproved in operability also in this respect. In addition, with thearrangement of the operation input device at the position along thedirection intersecting the direction along which the lock device and theshoe fixing device are arranged, the operation input device can beefficiently arranged without affecting to the necessary space for thelock device and the shoe fixing device. As a result, it is possible toefficiently arrange the operation input device, the lock device and theshoe fixing device with respect to the housing.

In a still further aspect of the present teachings, the electric toolmay include a motor for generating a rotational drive force, an outputshaft rotatably driven by the rotational drive force of the motor, and atool holder disposed at a front portion of the output shaft andconfigured to hold an end tool. The electric tool may further include anadjustment base capable of adjusting a machining range of the end tool,and a support housing configured to support the output shaft. An airflow passage may be defined in the support housing, so that air can flowin an axial direction along the air flow passage.

With this arrangement, air may flow in the axial direction along the airflow passage defined in the support housing. Therefore, it is possibleto direct air toward various components, whose positions may bedetermined with respect to the position of the output shaft. Hence, itmay be possible to blow off the dust from these components before thedust falls on these components. In addition, because the dust may beblown in the axial direction of the output shaft, it may be possible toprevent the dust from accumulation within the support housing.

The air may be directed toward the tool holder or may flow to be appliedto the tool holder. With this arrangement, it may be possible to blowoff the dust from the tool holder before the dust falls on the toolholder. Therefore, it may be possible to ensure the proper operation ofthe tool holder.

The air flow passage may be defined between an outer circumferentialsurface of the output shaft and an inner circumferential surface of thesupport housing. With this arrangement, it may be possible to morereliably prevent the dust from accumulation within the housing.

The electric tool may further include an operation mechanism foroperating the tool holder, and the air may be directed toward theoperation mechanism. With this arrangement, it may be possible to blowoff the dust from the operation mechanism before the dust falls on theoperation mechanism. Therefore, it may be possible to ensure the properoperation of the operation mechanism.

The electric tool may further include a discharge opening provided at afront portion of the support housing, and the air may flow from thedischarge opening in at least a direction forwardly along the axialdirection of the output shaft.

With this arrangement, it may be possible to efficiently blow off thedust from a region on the front side of the support housing, where thedust is prone to be produced. Therefore, the produced dust may beprevented from accumulation. As a result, it is possible to reduce anuncomfortable feeling given to the operator by the dust. Eventually, theoperator can comfortably use the electric tool.

The air may be directed to flow toward a side of an outer circumferenceof the adjustment base. Because the air may flow through points aroundthe outer circumference of the adjustment base, the dust produced duringthe use of the electric tool may be blown toward the outercircumferential side of the adjustment base. Hence, the dust may not beflown toward the operator. As a result, it is possible to reduce anuncomfortable feeling given to the operator by the dust. Eventually, theoperator can comfortably use the electric tool also in this respect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an electric tool according to a firstembodiment of the present invention;

FIG. 2 is a vertical sectional view of the electric tool showing theinternal structure of the electric tool;

FIG. 3 is a horizontal sectional view of the electric tool showing theinternal structure of the electric tool;

FIG. 4 is an enlarged perspective view of the front portion of theelectric tool;

FIG. 5 is an enlarged view of a part of FIG. 2 showing an output sectionof the electric tool:

FIG. 6 is a view similar to FIG. 5 but showing the state where anoperation mechanism has been operated;

FIG. 7(a) is a perspective view of an insert shown in FIGS. 5 and 6;

FIG. 7(b) is a sectional view of the insert taken along lineVII(b)-VII(b) in FIG. 7(a);

FIG. 8(a) is a perspective view of a nut shown in FIGS. 5 and 6;

FIG. 8(b) is a sectional view of the nut taken along lineVIII(b)-VIII(b) in FIG. 8(a);

FIG. 9 is an enlarged view of a part of FIG. 4 showing an engagementkeeping mechanism;

FIG. 10 is an enlarged view of a part of FIG. 5 showing the engagementkeeping mechanism;

FIG. 11 is an enlarged view of a part of FIG. 6 showing the engagementkeeping mechanism;

FIG. 12 is an enlarged perspective view of the front portion of theelectric tool showing the streams of discharge air by thick lines;

FIG. 13 is an enlarged view of a part of FIG. 2 showing a region aroundthe output section of the electric tool;

FIG. 14 is an enlarged view of a part of FIG. 3 showing the outputsection of the electric tool;

FIG. 15 is a view similar to FIG. 14 but showing the state where theoperation mechanism has been operated;

FIG. 16 is a front view of the electric tool;

FIG. 17 is a sectional view taken along line XVII-XVII in FIG. 2;

FIG. 18 is a sectional view taken along line XVIII-XVIII in FIG. 2;

FIG. 19 is a sectional view taken along line XIX-XIX in FIG. 2;

FIGS. 20(a) and 20(b) show front views of a nut and an engaging member,respectively, according to a first example;

FIGS. 21(a) and 21(b) show front views of a nut and an engaging member,respectively, according to a second example;

FIG. 22 is an enlarged view of the rear portion of the electric toolshowing a rear part of a second air flow passage;

FIG. 23 is an enlarged view of the front portion of the electric toolshowing a front part of the second air flow passage;

FIG. 24 is a side view of an electric tool according to a secondembodiment;

FIG. 25 is an enlarged perspective view of the electric tool shown inFIG. 24;

FIG. 26 is a horizontal sectional view of the electric tool shown inFIG. 24;

FIG. 27 is a view similar to FIG. 24 but showing the state where thefixation of a shoe has been released;

FIG. 28 is a view similar to FIG. 25 but showing the state where thefixation of the shoe has been released;

FIG. 29 is a view similar to FIG. 26 but showing the state where thefixation of the shoe has been released;

FIG. 30 is a side view of an electric tool according to a thirdembodiment;

FIG. 31 is an enlarged perspective view of the electric tool shown inFIG. 30;

FIG. 32 is a horizontal sectional view of the electric tool shown inFIG. 30;

FIG. 33 is a view similar to FIG. 30 but showing the state where thefixation of a shoe has been released;

FIG. 34 is a view similar to FIG. 31 but showing the state where thefixation of the shoe has been released; and

FIG. 35 is a view similar to FIG. 32 but showing the state where thefixation of the shoe has been released.

DETAILED DESCRIPTION OF THE INVENTION

Each of the additional features and teachings disclosed above and belowmay be utilized separately or in conjunction with other features andteachings to provide improved electric tools. Representative examples ofthe present invention, which examples utilize many of these additionalfeatures and teachings both separately and in conjunction with oneanother, will now be described in detail with reference to the attacheddrawings. This detailed description is merely intended to teach a personof skill in the art further details for practicing preferred aspects ofthe present teachings and is not intended to limit the scope of theinvention. Only the claims define the scope of the claimed invention.Therefore, combinations of features and steps disclosed in the followingdetailed description may not be necessary to practice the invention inthe broadest sense, and are instead taught merely to particularlydescribe representative examples of the invention. Moreover, variousfeatures of the representative examples and the dependent claims may becombined in ways that are not specifically enumerated in order toprovide additional useful examples of the present teachings. Variousexamples will now be described with reference to the drawings.

Embodiments will now be described with reference to the drawings, inwhich three different embodiments are shown. Electric tools of theseembodiments are those called cut-out tools that can be used formachining operations, such as a cut-out operation, of plaster boards.

<First Embodiment>

An electric tool 10 according to a first embodiment will now bedescribed with reference to FIGS. 1 to 7. For the purpose ofillustration, the upward, downward, forward, reward, leftward andrightward directions with respect to the electric tool 10 are determinedas shown in these figures. In FIG. 1, the electric tool 10 is shown inthe state where a rechargeable battery 15 has been removed from a toolmain body 11. The electric tool 10 may be designed as a hand-held typeone that can be held by a hand or hands of the operator during the use.

Referring to FIGS. 1 to 4, the electric tool 10 may generally includethe tool main body 11, the rechargeable battery 15 and a shoe 17. Thetool main body 11 may have a tubular housing including a motor housing21 serving as a housing of a drive section 20, and a front housing 31serving as a housing of an output section 30. Each of the motor housing21 and the front housing 31 may have a tubular shape and may extend in aforward and rearward direction. A motor 25 with brushes may be disposedwithin the motor housing 21. In the following description, the forwardand rearward direction, the upward and downward direction (verticaldirection) and the left and right direction with respect to the electrictool 10 will be also called a first direction, a second direction and athird direction, respectively. Therefore, the motor housing 21 mayextend in the first direction. The second direction may intersect thefirst direction. The third direction may intersect both the first andsecond directions.

The rechargeable battery 15 may be mounted to the tool unit body 11 andmay serve as a power source. When the rechargeable battery 15 has beendischarged as a result of use, a dedicated battery charger (not shown)can recharge the rechargeable battery 15. The tool may body 11 has abattery mount portion 13 at its rear end. The rechargeable battery 15can be mounted to the battery mount portion 13 as it is slidsubstantially in the upward and downward direction along the batterymount portion 13. In this way, the rechargeable battery 15 can bemounted to the battery mount portion 13 as it is slid in the verticaldirection that intersects the forward and rearward direction (i.e., thefirst direction).

The shoe 17 is positioned at a position forwardly of the front end ofthe output spindle 35. By determining the position of the shoe 17relative to the tool unit body 11, a protruding length (protrudingdistance) of a tool bit B from the shoe 17 can be determined. Morespecifically, the position of the shoe 17 can determine the protrudinglength of the tool bit B that is mounted to a bit mount mechanism 41.The protruding length of the tool bit B may relate to a range of thetool bit B used for the machining operation. For this reason, the shoe17 is disposed at the front end of the tool main body 11 and issupported by the front housing 31.

The shoe 17 may include a shoe body 171 and a mount portion 172. Theshoe body 171 is positioned to oppose to a workpiece. The mount portion172 is mounted to the tool main body 11 by means of a finger screw 18.The shoe body 171 serves as an adjustment base as will be explainedlater. The show body 171 extends in a direction intersecting theextending direction of the mount portion 172. The mount portion 172 mayinclude an elongated slot 173 elongated in the forward and rearwarddirection. The mount portion 172 may slide under the guide of a guidemember 174 that is fixed in position relative to the front housing 31.More specifically, the guide member 174 may be fixed to the fronthousing 31 by means of screws. Guide ribs 175 may be formed on the guidemember 174 and may guide the mount portion 172 to allow the slidingmovement of the mount portion 172 in the forward and rearward direction.In this way, the shoe 17 is configured to be able to change its positionrelative to the front housing 31 as it moves in the forward and rearwarddirection.

The shoe 17 can be slid in the forward and rearward direction relativeto the tool main body 11 to a suitable position, where the shoe 17 maybe fixed in position by using the finger screw 18. More specifically, asthe finger screw 18 is rotated in a tightening direction, the mountportion 172 of the shoe 17 may be pressed against the guide member 174,so that the mount portion 172 of the shoe 17 may be fixed in positionrelative to the guide member 174 by the finger screw 18. In this way,the shoe 17 can be fixed in position relative to the tool main body 11.Therefore, the finger screw 18 serves as a shoe fixing device for fixingthe shoe 17 in position. The position fixing operation of the shoe 17may be performed after the position of the shoe 17 is adjusted relativeto the tool main body 11 having the motor housing 12.

The tool bit B that may be mounted to the bit mount mechanism 41 mayprotrude forwardly from the shoe 17. The position of the shoe 17 can beadjusted as described above. The protruding length of the tool bit B maybe determined according to the position of the shoe 17. As describedabove, the tool bit B serves as an end tool. In this embodiment, theposition adjusting direction (forward and rearward direction) of theshoe 17 perpendicularly intersects the mounting direction (verticaldirection) of the rechargeable battery 15.

The tool main body 11 will now be described. The tool main body 11 maybe generally divided into the drive section 20 and the output section30. The drive section 20 mainly serves to generate a drive force. Theoutput section 30 serves to support the output spindle 35 that isrotatably driven. The drive section 20 extends over the rear portion andthe intermediate portion of the tool main body 11 and may convert theelectric power to the rotational drive force. The drive section 20includes the motor housing 21 and also includes various componentsdisposed in the motor housing 21. The motor housing 21 has left andright halves each formed by a molding process. The battery mount portion13 is positioned at the rear end of the motor housing 21. Within themotor housing 21, a controller 22, a switch 23, the motor 25 and a fan29 may be disposed and arranged in this order in the forward direction.The controller 22 may control the supply of electric power from therechargeable battery 15. The switch 23 may receive an operation inputfrom a slide switch 231. The slide switch 231 is exposed to the outsideof the motor housing 21 and can be slid in forward and rearwarddirections. More specifically, the slide switch 231 is elongated in theforward and rearward direction. As the operator shifts the slide switch231 in the forward direction, the rear end surface of the slide switch231 moves the rear end of an operation element (not shown) coupled tothe switch 23, so that an on operation input can be made for turning onthe switch 23. The slide switch 231 serves as an operation input devicethat provides an operation input relating to the rotary drive of themotor 25. The slide switch 231 is disposed at the upper portion of themotor housing 21. In other words, the slide switch 231 is disposed atthe upper portion in the vertical direction of the motor housing 21. Thevertical direction with respect to the motor housing 21 intersects theleft and right direction.

The motor 25 may have a construction that is generally used for knownmotors having brushes. The motor 25 has a motor shaft 26 that is drivento rotate. A rear bearing 27 and a front bearing 28 rotatably supportthe motor shaft 26. The tool bit B may be mounted to the output spindle35 that is coupled to the front portion of the motor shaft 26. The motorhousing 21 support the rear bearing 27. The front housing 31 supportsthe front bearing 28.

The fan 29 is mounted to the motor shaft 26. The fan 29 may be acentrifugal fan. As the fan 29 rotates, the air may flow in the forwarddirection within the motor housing 21. The flow of air produced by thefan 29 serves as a motor cooling air that may mainly cool the controller22, the switch 23 and the motor 25 in this order. More specifically, theair may be introduced into the motor housing 21 via air inlet openings211 formed in the rear portion of the motor housing 21. The air may thenflow through the controller 22, the switch 23 and the brush motor 25 forcooling them in this order. Thereafter, the air may flow through the fan29 to enter inside of the front housing 31. After entering inside of thefront housing 31, the air may be blown out of the front housing 31 viaair-blow openings 36 disposed at the front portion of the electric tool10 as will be explained later, so that the air can be discharged to theoutside. In this way, in this embodiment, an air flow passage is formedfor the flow of air, so that the air is introduced into the tool manbody 11 via the inlet openings 211 and is thereafter discharged to theoutside via the air-blow openings 36 by the operation of the fan 29. Themotor cooling air may be also called a discharge air. The air-blowopenings 36 serve as a discharge opening provided at the front portionof the front housing 31.

The output section 30 positioned on the front side of the drive section20 will now be described. FIG. 5 is an enlarged sectional view showingan internal structure of the output section 30 shown in FIG. 2. FIG. 6shows an enlarged sectional view similar to FIG. 5 but showing theoperation of an operation mechanism 60 shown in FIG. 5.

As shown in FIGS. 5 and 6, the output section 30 may be configured as afront section of the tool main body 11. The output section 30 mainlyserves to hold and rotate the tool bit B. The output section 30generally includes the front housing 31, the output spindle 35 and thebit mount mechanism 41. As shown in FIG. 4, the front housing 31 servingas a housing of the output section 30 is attached to the front end ofthe motor housing 21 by means of four screws 19. In this way the fronthousing 31 is fixed in position relative to the motor housing 21. Unlikethe motor housing 21 divided into two halves, the front housing 31 is aone-piece member made of metal and may be formed by a forming process.The front housing 31 has front and rear openings. Therefore, the motorshaft 26 may be inserted into the front housing 31 from the rear side,and the output spindle 35 may be inserted into the front housing fromthe front side to protrude therefrom. In this way, the front housing 31serves as a support housing for supporting the output spindle 35.

As shown in FIGS. 4 and 12, the air-blow openings 36 is formed in thefront portion of the front housing 31 for blowing out the air to theoutside. In this embodiment, four air-blow openings 36 are provided atequal intervals along the circumferential direction of the front portionof the front housing 31 (see FIG. 16). More specifically, the air-blowopenings 36 are arranged and configured such the air blown from theair-blow openings 36 is directed toward the shoe body 171 of the shoe17, in particular toward the front portion of the shoe body 171 whichmay be opposed to a workpiece to be machined by the tool bit B. In otherwords, the air blown out of the air-blow openings 36 is directed towardthe workpiece that is machined by the tool bit B. The air-blowingdirections (discharge directions) of the air from the four air-blowopenings 36 are directed such that air streams pass through points onthe outer side of an outer circumferential edge 275 of the front portionof the shoe body 171 and are then directed radially outward as indicatedby thick lines (see lines F2 in FIG. 12).

As shown in FIGS. 5 and 14, the mount portion 172 of the shoe 17 ismounted to the right side surface of the front housing 31 by means ofthe finger screw 18. As shown in FIGS. 3 and 14, a shaft lock mechanism37 may be provided on the left side portion of the front housing 31. Asviewed from the front side or the rear side, the arrangement position ofthe finger screw 18 and the arrangement position of the shaft lockmechanism 37 are substantially symmetrical with each other with respectto the central axis of the front housing 31 that extends in the forwardand rearward direction (first direction). In other words, as viewed fromthe front side or the rear side, the finger screw 18 and the shaft lockmechanism 37 are arranged along the left and right direction thatintersects both the forward and rearward direction and the verticaldirection. The shaft lock mechanism 37 may be used for locking theoutput spindle 35 not to rotate about the axis of the output spindle 35before the tool bit B is mounted to the bit mount mechanism 41 that willbe explained later. More specifically, the shaft lock mechanism 37serves as a lock mechanism for preventing rotation of the bit mountmechanism 41 relative to the front housing 31. The shaft lock mechanism37 may include an actuation member 38 and a biasing spring 39. Theactuation member 38 includes an actuation main body 381 and an operationcover 382. The actuation main body 381 includes a pin. The operationcover 382 is coupled to the actuation main body 381 and may be operableby the operator. As the operator presses the operation cover 382, theactuation main body 381 may move radially inward, so that the pin may beinserted into any one of four insertion holes formed in the outputspindle 35. The biasing spring 39 serves to normally bias the pin in thedirection radially outward, i.e. a direction away from the insertionhole. Therefore, the pressing operation of the operation cover 382 ofthe actuation member 38 may be performed against the biasing force ofthe biasing spring 39. When the pin is inserted into one of theinsertion holes of the output spindle 35, the output spindle 35 may beprevented from rotation. In this way, the shaft lock mechanism 37 servesto prevent rotation of the output spindle 35.

As shown in FIGS. 5 and 14, a front end 261 of the motor shaft 26 mayextend into the front housing 31 and may be press-fitted into a rearfitting hole 351 formed in the rear end of the output spindle 35, sothat the output spindle 35 can rotate together with the motor shaft 26.The output spindle 35 may be called an output shaft. A front fittinghole 352 may be formed in the front end of the output spindle 35. Aninsert 45 that will be explained later may be press-fitted into thefront fitting hole 352 from its front side. A male thread portion 353 isformed on a part of the outer surface of the output spindle 35, intowhich the insert 45 is press-fitted. The male thread portion 353 canmesh with a female thread portion 513 of a nut 51 that will be explainedlater. The output shaft 35, with which the motor shaft 26 and the insert45 are integrated, is rotatably supported by the front bearing 28. Thefront housing 31 fixedly supports the front bearing 28.

The bit mount mechanism 41 provided on the output spindle 35 will now bedescribed. The bit mount mechanism 41 may be called a tool holder or atool mount device. The bit mount mechanism 41 may be also called a bitfixing device. The bit mount mechanism 41 can be used for mounting thetool bit B to the output spindle 35 that is rotatably driven. The bitmount mechanism 41 generally includes the insert 45 and the nut 51. Thenut 51 serves as a fastener.

The bit mount mechanism 41 may rotate as the motor 25 rotates. In orderto hold the tool bit B, the bit mount mechanism 41 protrudes forwardfrom the front end of the front housing 31. In this specification, thefront end side with respect to the electric tool 10 may be also calledone end side, and the rear end side opposite to the front end side withrespect to the electric tool 10 may be also called the other end side.

FIG. 7(a) shows a perspective view of the insert 45, and FIG. 7(b) showsa sectional view of the insert 45 taken along line VIIb-VIIb in FIG.7(a). FIG. 8(a) shows a perspective view of the nut 51, and FIG. 8(b)shows a sectional view of the nut 51 taken along line VIIIb-VIIIb inFIG. 8(a).

As shown in FIGS. 7(a) and 7(b), the insert 45 for press-fitting intothe front fitting hole 352 of the output spindle 35 is configured tohave a tubular shape into which the tool B can be fitted so as to bepositioned on the same axis as a central axis 40 (see FIG. 1) of theoutput spindle 35. More specifically, the insert 45 has a front opening46 communicating with the axial hole of the insert 45. The insert 45 canresiliently deform to decrease the inner diameter of the axial hole forholding the tool bit B inserted into the insert 45. More specifically, aplurality of slits 451 (four slits 451 are provided in this embodiment)are formed in the insert 45. The slits 451 extend in the axial directionof the central axis 40 and are spaced equally from each other in thecircumferential direction. With these slits 451, a plurality ofclaw-like portions (four claw-like portions in this embodiment) may beformed. The claw-like portions may be individually tiltable in aradially outer direction and a radially inner direction. A taperedportion 452 may be formed at the front end portion of the outercircumferential surface of the insert 45.

As shown in FIG. 5, the nut 51 may be positioned on the radially outerside of the insert 45. The nut 51 has a front opening 52, through whichthe tool bit B can be inserted. As shown in FIGS. 8(a) and 8(b), the nut51 includes a female thread portion 513 formed on its innercircumferential surface. The female threaded portion 513 may mesh withthe male thread portion 353 formed on the outer surface of the outputspindle 352. A diameter-decreasing portion 512 having an inclinationconforming to the inclination of the tapered portion 452 is formed onthe front end portion of the inner circumferential surface of the nut51. The diameter-decreasing portion 512 may contact or may not contactthe tapered portion depending on the meshing position of the femalethread portion 513 with the male thread portion 353. When the nut 51 isrotated in the thread-tightening direction relative to the outputspindle 35 in the state where the diameter-decreasing portion 512 is incontact with the tapered portion 452, the diameter-decreasing portion512 may apply a pressing force in the radially inward direction againstthe tapered portion 452 of the insert 45. Therefore, the front end ofthe insert 45 may receive a force in a diameter-decreasing direction. Inthis way, the tool bit B inserted into the insert 45 through the frontopening 46 may be held by the insert 45. More specifically, the innercircumferential surface of the insert 45 may be pressed against theouter circumferential surface of the tool bit B. At that time, the nut51 may be positioned at a tightening position (hereinafter called a bitholding position) against the insert 45.

When the nut 51 does not apply a pressing force against the insert 45(herein after called a bit releasing position), the inner diameter ofthe insert 45 may have a normal diameter value that is given when noload is applied to the insert 45. The bit releasing position of the nut51 is positioned on the front side of the bit holding position. When thenut 51 is positioned at the bit releasing position, thediameter-reducing portion 52 may not apply a pressing force in theradially inner direction against the tapered surface 452. Therefore, theinner circumferential surface of the insert 45 also may not be pressedagainst the outer circumferential surface of the tool bit B, so that theinsert 45 may not hold the tool bit B. Hence, the tool bit B can beremoved from and inserted into the insert 45 when the nut 51 ispositioned at the bit releasing position. In this way, thediameter-decreasing portion 512 can apply a force in the radially inwarddirection to the outer circumferential surface of the insert 45 so as tocause decrease in the inner diameter of the insert 45 depending on themeshing position of the female thread portion 513 with the male threadportion 353. The rotational axis of the nut 51 may be the same as therotational axis 40 of the output spindle 35.

The operation mechanism 60 for operating the bit mount mechanism 41 willnow be described. The operation mechanism 60 may be also called anoperation device or an operation section. As shown in FIGS. 5, 6, 14 and15, the operation mechanism 60 is provided at the front housing 31. Theoperation mechanism 60 generally includes an engaging member 61, astopper 71 and a biasing spring 75. As shown in FIG. 4, the engagingmember 61 has a substantially annular shape and generally includes aguide portion 62, a coupling portion 63 and an engaging portion 64. Theguide portion 62 serves as a guide for allowing a sliding movement ofthe engaging portion 64. The guide portion 62 has a double wallstructure so as to be opposed to a guide edge portion 32 of the fronthousing 31 from both the radially outer side and the radially innerside. The guide edge portion 32 protrudes forwardly from the front endof the front housing 31 and has a substantially circular ring shape.Therefore, the guide portion 62 includes an outer ring 621 and an innerring 622 each having a circular ring shape corresponding to the ringshape of the guide edge portion 32. The outer ring 621 and the innerring 622 are connected to each other by a turn-back portion 623 disposedon the front side thereof. The coupling portion 63 is disposed at therear end of the inner ring 622 of the guide portion 62. The stopper 71has a coupling portion 73 for coupling to the coupling portion 63. Morespecifically, the coupling portion 63 of the engaging member 61 has afemale coupling configuration that can be coupled to the couplingportion 73 having a male coupling configuration. The innercircumferential surface of the inner ring 622 may be configured as theengaging portion 64. The engaging portion 64 is formed so as to engagethe outer circumferential surface of the nut 51. Due to the engagementof the engaging portion 64 with the outer circumferential surface of thenut 51, the nut 51 may rotate together with the engaging portion 64about the rotational axis 40 (see FIGS. 5 and 14).

As shown in FIGS. 5 and 14, a rear end 624 of the outer ring 621 of theengaging member 61 is opposed to a front surface 311 of the fronthousing 31. The biasing spring 75 biases the engaging member 61 in therearward direction, i.e., a direction in which the rear end 624 of theouter ring 621 moves toward the front surface 311, so that the rearsurface of the turn-back portion 623 may contact the front end of theguide edge portion 32. At the same time, the rear end 624 of the outerring 621 may contact the front surface 211 of the front housing 31 ormay be positioned proximal to the front surface 211. Therefore, it maybe possible to prevent dust from entering within the front housing 31,in particular within the space where the biasing spring 75 is disposed.In addition, a projection 625 may be formed on the inner circumferentialsurface of the inner ring 622 of the engaging member 61 and may protruderadially inward therefrom. The projection 625 may contact the front endof the coupling portion 73 of the stopper 71 in the axial direction.Further, the outer circumferential surface of the coupling portion 73and the inner circumferential surface of the coupling portion 63 areopposed to each in the diametrical direction. Therefore, the projection625 may prevent dust from entering the space where the output spindle 35is provided, via a clearance formed between the inner circumferentialsurface of the coupling portion 63 and the outer circumferential surfaceof the coupling portion 73.

The stopper 71 also may have a substantially ring shape. The stopper 71generally includes the coupling portion 73 and an outer flange portion74. The outer flange portion 74 is configured to slidably contact theinner circumferential surface of the front housing 31. With this slidingcontact with the inner circumferential surface of the front housing 31,the stopper 71 and the engaging member 61 may be guided with respect tothe movement in the forward and rearward direction. The outer flangeportion 74 is configured to support one end of the biasing spring 75.The coupling portion 73 is configured as a male coupling that may befitted into the coupling portion 63 of the engaging member 61.Therefore, the stopper 71 is fixedly coupled to the engaging member 61through fitting between the coupling portion 73 and the coupling portion63. In this way, the stopper 71 serves as a part of the engaging member61. The outer flange portion 74 is disposed on the rear side of thecoupling portion 73. The rear end of the biasing spring 75 may contactthe outer flange portion 74. The biasing spring 75 may be a coil springor any other suitable resilient member and serves to bias the engagingmember 61 in a disengaging direction for disengagement of the engagingmember 61 from the bit mount mechanism 41. The biasing spring 75 is heldwithin the front housing 31 that supports the output spindle 35. Morespecifically, the biasing spring 75 is positioned between the guide edgeportion 32 of the front housing 31 and the inner ring 622 of theengaging member 61 with respect to the diametrical direction. The frontend of the biasing spring 75 may contact an inner flange portion 33 thatprotrudes radially inward from the guide edge portion 32 toward theinner ring 622. The inner flange portion 33 may be called a protrusionprotruding from the front housing 31. As described previously, the rearend of the biasing spring 75 may contact the outer flange portion 74. Inthis way, the biasing spring 75 serves to bias the engaging member 61and the stopper member 71 that is a member on the side of the engagingmember 61, in a rearward direction with respect to the tool main body11. The font end and the rear end of the biasing spring 75 may slidablycontact the inner flange portion 33 and the outer flange portion 74,respectively. The biasing direction of the biasing spring 75 that is oneof the components of the operation mechanism 60 is determined to beperpendicular to the biasing direction of the biasing spring 39 that isone of the components of the shaft lock mechanism 37.

The rearward movement of the engaging member 61 and the stopper 71caused by the biasing force of the biasing spring 75 may be stoppedthrough contact of the rear surface of the turn-back portion 623 withthe front end of the guide edge portion 32 as shown in FIGS. 5 and 14.The stop position of the engaging member 61 shown in FIGS. 5 and 14 isdetermined as a disengaging position (P1). When the engaging member 61is positioned at the disengaging position (P1), the engaging member 61does not engage the outer circumferential surface of the nut 51, so thatthe nut 51 may not rotate together with the engaging member 61. On theother hand, when the engaging member 61 moves forwardly so as to bepositioned at an engaging position (P2) shown in FIGS. 6 and 15, theengaging portion 64 of the engaging member 61 may engage the outercircumferential surface of the nut 51, so that the nut 51 can rotatetogether with the engaging member 61. The outer circumferential surfaceof the nut 51 may have a hexagonal shape in cross section.

In this way, the engaging portion 64 engages the outer circumferentialsurface of the nut 51 when the engaging member 61 is positioned at theengaging position (P2). The engaging position (P2) is spaced away fromthe disengaging position (P1) along the forward and rearward directionof the front housing 31. When the engaging member 61 is positioned atthe engaging position (P2), the nut 51 can rotate together with theengaging member 61 as the engaging member 61 rotates about therotational axis 40. In this way, by rotating the engaging member 61, thenut 51 may rotate to move relative to the insert 45 through the threadengagement with the output spindle 35. In this way, the disengagingposition (P1) and the engaging position (P2) are spaced from each otherin the forward and rearward direction along the rotational axis 40. Morespecifically, the engaging position (P2) is positioned forwardly of thedisengaging position (P1) along the rotational axis 40.

The inner circumferential surface of the engaging portion 64 of theengaging member 61 may have any cross sectional shape as long as it canengage the outer circumferential surface of the nut 51 with respect tothe rotational direction. FIGS. 20(a) and 20(b) show a first exampleregarding the engagement structure between the nut 51 and the engagingmember 61. In this example, the outer circumferential surface of the nut51 has a hexagonal shape as described above and as shown in FIG. 20(a),while the inner circumferential surface of the engaging portion 64 has abihexagonal shape as shown in FIG. 20(b). This example may beadvantageous because the engaging portion 64 can easily engage the nut51. FIGS. 21(a) and 21(b) show a second example regarding the engagementstructure between a nut 51′ and an engaging member 61′ having anengaging portion 64′. In this example, the outer circumferential surfaceof the nut 51′ has six protrusions 57 protruding radially outward fromthe outer circumferential surface and spaced equally from each other inthe circumferential direction. The inner circumferential surface of theengaging portion 64′ has twelve grooves spaced equally from each otherin the circumferential direction and each configured to conform to theshape of the protrusion 57. Also, this example may be advantageousbecause the engaging portion 64′ can easily engage the nut 51′.

An engagement keeping mechanism 80 will now be described. The engagementkeeping mechanism 80 is operable to keep the engaging member 64 at theengaging position (P2) where the engaging portion 64 of the engagingmember 61 engages the outer circumferential surface of the nut 51. Inthis embodiment, the engagement keeping mechanism 80 can keep theengaging member 64 at the engaging position (P2) as long as theengagement keeping mechanism 80 is not operated for releasing.

The engagement keeping mechanism 80 is provided at a position proximalto the front housing 31. The engagement keeping mechanism 80 is shown inan enlarged view in FIG. 9 that is an enlarged view of a part of FIG. 4.The cross sectional view of the engagement keeping mechanism is shown inFIG. 10 that is an enlarged view of a part of FIG. 5. The crosssectional view of the engagement keeping mechanism 80 is also shown inFIG. 11 that is an enlarged view of a part of FIG. 6. The engagementkeeping mechanism 80 is disposed at the outer ring 621 of the engagingmember 61. The engagement keeping mechanism 80 generally includes apivotal support 81 mounted to or formed on the outer ring 621, anengagement keeping member 83 pivotally supported by the pivotal support81, and a biasing spring 87 for biasing the engagement keeping member 83toward an engaging keeping position. As shown in FIG. 9, the pivotalsupport 81 protrudes outwardly from the outer circumferential surface ofthe outer ring 621. The pivotal support 81 includes a support pin 82that pivotally supports the engagement keeping member 83.

As shown in FIGS. 10 and 11, the engagement keeping member 83 may bebent to have a substantially L-shape in cross section and may include anoperation wall portion 84 and a contact wall portion 85. Similar to theouter circumferential surface of the outer ring 621, the operation wallportion 84 may be exposed to the outside for enabling access by theoperator. More specifically, the operation wall portion 84 is configuredsuch that the operator can push the operation wall portion 84 by using afinger(s). One end of the biasing spring 87 contacts the front portionof the operation wall portion 84. The biasing spring 87 may be a coilspring and biases the operation wall portion 84 toward the outside. Thebiasing member 87 is received within a retaining recess 88 formed in theouter ring 621, so that the other end of the biasing member 87 contactsthe bottom of the retaining recess 88. The contact wall portion 85 isformed on the rear side of the operation wall portion 84 and isconfigured to extend into inside of the outer ring 621. To this end, thecontact wall portion 85 extends in a direction intersecting an extendingdirection of the operation wall portion 84. As shown in FIGS. 10 and 11,the contact wall portion 85 extends into inside of the outer ring 621 inthe radially inward direction so as to be able to contact with a frontend 34 of the guide edge portion 32. In this connection, a communicationhole 89 may be formed in the outer ring 621, so that the contact wallportion 85 can extend into inside of the outer ring 621 via thecommunication hole 89. The communication hole 89 may be formed, forexample, by cutting out a part of the outer ring 621 to extend intoinside and outside of the outer ring 621. The contact wall portion 85has a radially inner end 851 inclined rearwardly in the radially outwarddirection for contacting the front end 34 of the guide edge portion 32in the forward and rearward direction. In this way, as the engagementkeeping member 83 pivots about the support pin 82 by the biasing forceof the biasing spring 87, the radially inner end 851 may be positionedfor contacting with the front end 34 of the guide edge portion 32.

When the engaging member 61 is positioned at the disengaging position(P1), the contact wall portion 85 of the engagement keeping member 83may not contact the front end 34 of the guide edge portion 32 but maycontact the outer circumferential surface of the guide edge portion 32as shown in FIG. 10. In the state shown in FIG. 10, the operation wallportion 84 of the engagement keeping member 83 extends substantiallyparallel to the outer circumferential surface of the outer ring 621. Onthe other hand, when the engaging member 61 is positioned at theengaging position (P2), the radially inner end 851 of the contact wallportion 85 of the engagement keeping member 83 contacts the front end 34of the guide edge portion 32 as shown in FIG. 11. The position of thecontact wall portion 85 shown in FIG. 11 may be kept by the biasingforce of the biasing spring 87, so that the engaging member 61 may beprevented from moving from the engaging position (P2) to the disengagingposition (P1). In this way, the engaging member 61 may be kept at theengaging portion (P2). In this state, the operation wall portion 84 ofthe engagement keeping member 83 extends to obliquely intersect theouter circumferential surface of the outer ring 621. In addition, as theengaging member 61 moves from the disengaging position (P1) to theengaging position P(2), the engagement keeping member 83 automaticallypivots from the position shown in FIG. 10 to the position shown in FIG.11 by the biasing force of the biasing spring 87.

Therefore, the operator can determine whether the engaging member 61 ispositioned at the disengaging position (P1) or the engaging position(P2) based on the extending direction of the operation wall portion 84of the engagement keeping member 83 relative to the outercircumferential surface of the outer ring 621. Thus, the operator candetermine that the engaging member 61 is positioned at the disengagingposition (P1) if the operation wall portion 84 of the engagement keepingmember 83 extends substantially parallel to the outer circumferentialwall of the outer ring 621. On the other hand, the operation candetermine that the engaging member 61 is positioned at the engagingposition (P2) if the operation wall portion 84 of the engagement keepingmember 83 extends in a direction obliquely intersecting the outercircumferential wall of the outer ring 621. In this way, the operatorcan determine whether or not the engaging member 61 engages the bitmount mechanism 41 based on the extending direction of the engagementkeeping member 83 including the operation wall portion 84 relative tothe outer circumferential surface of the outer ring 621. Therefore, theengagement keeping member 83 including the operation wall portion 84serves as a determination device for determining the position of theengaging member 61. In one embodiment, a marker(s) indicating theextending direction of the operation wall portion 84 of the engagementkeeping member 83 may be provided for helping visual recognition of thedisengaging position (P1) and/or the engaging position (P2). With thisarrangement, the operator can further easily reliably determine theextending direction of the operation wall portion 84. Hence, theoperator can further easily reliably determine the position of theengaging member 61. In addition, the engagement keeping member 83including the operation wall portion 84 may serve as a part of anindicator that indicates the extending direction of the operation wallportion 84. For example, an output device such as a lamp indicator maybe provided for outputting information regarding the extending directionof the operation wall portion 84, so that the operator can more easilydetermine the position of the engaging member 61.

As described previously, the air flow passage is formed for the flow ofair that is introduced into the tool man body 11 via the inlet openings211 and thereafter discharged to the outside via the air-blow openings36 by the operation of the fan 29. This air flow passage will behereinafter called a first air flow passage. In the case of thisembodiment, the air introduced into the tool man body 11 via the inletopenings 211 by the operation of the fan 29 may be also discharged via asecond air flow passage 180 that does not include the air blow openings36. The second air flow passage 180 includes a front blow opening 188provided between the bit mount mechanism 41 and the operation mechanism60 (see FIG. 23) for discharging air from the tool man body 11. FIGS. 22and 23 respectively show a rear part and a front part of the second airflow passage 180 in an enlarged scale. Within the motor housing 21, thesecond flow passage 180 runs along the same route as the first air flowpassage. Thus, as the fan 29 rotates, air may be introduced into themotor housing 21 via the inlet openings 211 so as to serve as a coolingair that cools the controller 22, the switch 23 and the motor 25 in thisorder. After passing through the fan 29, the air may flow into the fronthousing 31. In this way, a passage part 181 within the motor housing 21of the second air flow passage 180 runs along the routes indicated bythick solid lines in FIG. 22. The passage part 181 runs through variouscomponents (including the controller 22, the switch 23 and the motor 25,etc.) disposed within the motor housing 21. In other words, the passagepart 181 is defined by the motor housing 21, controller 22, the switch23, the motor 25, etc. After leaving the passage part 181, the air mayflow into the fan 29 that may be called an air blowing device. Afterflowing through the fan 29, the air may enter the front housing 31.Thus, the second air flow passage 180 includes a passage part 182 withinthe front housing 31. The passage part 182 is indicated by thick solidlines in FIG. 23. The passage part 182 runs through various components(including the output spindle 35, the front bearing 28, the bit mountmechanism 41, the operation mechanism 60, etc.) disposed within thefront housing 31. In other words, the passage part 182 is defined by thefront housing 31, the output spindle 35, the front bearing 28, the bitmount mechanism 41, the operation mechanism 60, etc.

The second air flow passage 180 will be described in more detail. Asshown in FIGS. 19 and 23, the air blown from the fan 29 may flowforwardly after passing through air passage holes 185. The air passageholes 185 may be formed, for example, by cutting-out portions of thefront housing 31 that supports the front bearing 28. In this embodiment,a pair of air passage holes 185 are formed so as to be positioned inpoint symmetry with respect to the output spindle 35 such that one ofthe air passage holes 185 is positioned on the upper side of the outputspindle 35 and the other is positioned on the lower side of the outputspindle 35. Therefore, the front bearing 28 is supported by a portion ofthe front housing 31, which portion does not include the air passageholes 185. As shown in FIGS. 18 and 23, after passing through the airpassage holes 185, the air may flow into air passage holes 186. The airpassage holes 186 may be formed, for example, by cutting-out portions ofthe outer flange portion 74 of the stopper 71. Two pairs of air passageholes 186 may be formed to be positioned in point symmetry with respectto the output spindle 35 such that one of two pairs of the air passageholes 186 is positioned on the upper side of the output spindle 35 andthe other is positioned on the lower side of the output spindle 35.Therefore, the air passage holes 186 in one of the two pairs arepositioned obliquely leftward and rightward on the upper side of theoutput spindle 35, while the air passage holes 186 in the other of thetwo pairs are positioned obliquely leftward and rightward on the lowerside of the output spindle 35. As shown in FIGS. 17 and 23, afterpassing though the air passage holes 186, the air may flow into an airpassage gap 187 formed between the bit mount mechanism 41 and theoperation mechanism 60. More specifically, the air passage gap 187 isformed between the outer circumferential surface of the nut 51 of thebit mount mechanism 41 and the inner circumferential surface of theengaging member 61 of the operation mechanism 60. The air passage gap187 extends throughout the entire circumferential length of the innercircumferential surface of the engaging member 61. In this way, the airblown from the fan 29 may flow through the air passage holes 185, theair passage holes 186 and the air passage gap 187 in this order in theaxial direction of the output spindle 35. In other words, an air passagespace is defined between the outer circumferential surface of the outputspindle 35 and the inner circumferential surface of the front housing 31that supports the output spindle 35. The air may flow through the airpassage space in the axial direction of the output spindle 35 toward thebit mount mechanism 41 and the operation mechanism 60 disposed on thefront end side so as to reach to the bit mount mechanism 41 and theoperation mechanism 60.

As shown in FIG. 16, the externally exposed end (front end) of the airpassage gap 187 may define the front blow opening 188. The front blowopening 88 serves as a discharge opening for communication betweeninside and outside of the front housing 31. The front blow opening 188is opened at the front portion of the front housing 31. Morespecifically, the front blow opening 188 is positioned between the outercircumferential surface of the nut 51 of the bit mount mechanism 41 andthe inner circumferential surface of the engaging member 61 of theoperation mechanism 60 as described in connection with the air passagegap 187. The front blow opening 188 is configured such that the airblown out of the front blow opening 188 may flow in the axial directionof the output spindle 35 as shown in FIG. 12. In this way, the air mayflow forwardly in the axial direction of the output spindle 35 from thefront blow opening 188. This flow direction of air from the front blowopening 188 may be called an externally discharging direction of theair. As shown in FIG. 23, the open area of the front blow opening 188gradually increases in the forward direction. Therefore, the air blownfrom the front blow opening 188 may be directed toward the outercircumference of the shoe 17. More specifically, the stream of air blownfrom the front blow opening 188 may be enlarged outwardly toward theouter circumferential edge 275 of the front portion of the show body 171(see thick lines (F1)).

According to the electric tool 10 of the above embodiment, therechargeable battery 15 can be mounted to the battery mount portion 13as it is slid relative to the battery mount portion 13 in a directionvertically downward perpendicular to the forward and rearward direction.In this way, the rechargeable battery 15 can be mounted as it is slid inthe vertical direction that is perpendicular to the forward and rearwarddirection, along which the major axis (i.e., the axis of the motorhousing 21 or the front housing 31) of the electric tool 10 may extend.Therefore, the mounting operation of the rechargeable battery 15 can beeasily performed. Hence, the electric tool 10 may be improved in itsoperability. The sliding direction of the rechargeable battery 15 maynot be limited to the vertical direction but may be any of directionsperpendicular to the major axis of the electric tool 10 or may be any ofdirections intersecting the major axis direction.

In addition, the position of the shoe 17 can be changed relative to thetool main body 11 (motor housing 21) by moving the shoe 17 in theforward and rearward direction (first direction). Therefore, the shoe 17may be configured to extend in the same direction as the extendingdirection of the front housing 31. Therefore, it may be possible toconfigure that the electric tool 10 has a relatively small thickness atthe region of the shoe 17. Hence, the electric tool 10 may be improvedin its operability also in this respect.

Further, the shaft lock mechanism 37 and the finger screw 18 arepositioned at positions symmetrical with each other with respect to thecentral axis of the motor housing 21 that extends in the forward andrearward direction. Therefore, it is possible to reduce the size in theforward and rearward direction of the electric tool 10 at the regionaround the shaft lock mechanism 37 and the finger screw 18. Hence, it ispossible to reduce the length of the electric tool 10. As a result, theelectric tool 10 may be improved in its operability also in thisrespect.

Further, as viewed from the front side or the rear side, the arrangementdirection of the shaft lock mechanism 37 and the finger screw 18 is setto be the left and right direction that intersects both the forward andrearward direction and the vertical direction. Therefore, the shaft lockmechanism 37 and the finger screw 18 may be efficientlythree-dimensionally arranged. Hence, it is possible to reduce the sizeof the electric tool 10 at the region around the shaft lock mechanism 37and the finger screw 18.

Furthermore, with the electric tool 10 of this embodiment, the passagepart 182 of the second air flow passage 180 is formed within the fronthousing 31 that supports the output spindle 35. Therefore, the motorcooling air produced by the fan 29 can be fed along the passage part182. Because the passage part 182 is configured to guide the air alongthe axial direction of the output spindle 35, the air may be directedtoward the bit mount mechanism 41 and the operation mechanism 60arranged in association with the output spindle 35. Therefore, the dustmay be blown off from these mechanisms (the bit mount mechanism 41 andthe operation mechanism 60) before the dust falls on them. Hence, it ispossible to ensure that these mechanisms reliably properly operate. Inaddition, because the dust may be blown in the axial direction of theoutput spindle 35, it may be possible to prevent dust from accumulationwithin the front housing 31. Further, the discharge air may be directedtoward the bit mount mechanism 41 due to the guide of air between theoutput spindle 35 and the front housing 31 supporting the output spindle35. Therefore, the dust may be blown off from the bit mount mechanism 41before the dust falls on the same. Hence, it is possible to ensure thatthe bit mount mechanism 41 reliably properly operates also in thisrespect. Furthermore, because the passage part 182 of the second airflow passage 180 is defined between the outer circumferential surface ofthe output spindle 35 and the inner circumferential surface of the fronthousing 31, the dust may be prevented from entering the front housing31. Therefore, it may be possible to prevent dust from accumulationwithin the front housing 31 also in this respect. Furthermore, becausethe air may be directed to the operation mechanism 60 that is providedfor operating the bit mount mechanism 41, the dust may be blown off fromthe operation mechanism 60 before the dust falls on the same. Hence, itis possible to ensure that the operation mechanism 60 reliably properlyoperates also in this respect.

Furthermore, the front blow opening 188 and the air-blow openings 36serving as air discharge openings are provided at the front portion ofthe front housing 31. Because the front blow opening 188 and theair-blow openings 36 are configured such that air flows forwardly fromthese openings in the axial direction of the output spindle 35, it maybe possible to efficiently blow off the dust from a region on the frontside of the front housing 31, where the dust is prone to be produced.Therefore, the produced dust may be prevented from accumulation. Hence,it may be possible to prevent the dust from accumulation. As a result itis possible to reduce an uncomfortable feeling given to the operator bythe dust. Eventually, the operator can comfortably use the electric tool10.

Furthermore, the air blown from the front blow opening 188 and the airblown from the air-blow openings 36 may flow through points around theouter circumferential edge 275 of the front portion of the shoe body 171of the shoe 17. Therefore, the dust produced during the use of theelectric tool 10 may be blown toward the outer circumferential side ofthe shoe body 171. Hence, the dust may not be flown toward the operator.As a result it is possible to reduce an uncomfortable feeling given tothe operator by the dust. Eventually, the operator can comfortably usethe electric tool 10 also in this respect. More specifically, asindicated by thick lines (F1) in FIGS. 12 and 23, the air blown from thefront blow opening 188 may flow through points near and inside of theouter circumferential edge 275 of the front portion of the shoe body 171of the shoe 17. Therefore, it may be possible to blow the dust towardthe outer circumferential side of the shoe body 171. In addition, asindicated by thick lines (F2) in FIGS. 12 and 23, the air blown from thefour air-blow openings 36 disposed at the front portion of the fronthousing 31 may flow through points near and outside of the outercircumferential edge 275 of the front portion of the shoe body 171 ofthe shoe 17 in such a manner that the air streams are curved radiallyoutward around the outer circumferential edge 275. Therefore, it may bepossible to blow the dust toward the outer circumferential side of theshoe body 171 with a large force. Hence, the operator can easily performthe operation of the electric tool 10.

<Second Embodiment>

A second embodiment will now be described with reference to FIGS. 24 to29. FIG. 24 shows a side view of an electric tool 10A according to thesecond embodiment. The electric tool 10A is different from the electrictool 10 of the first embodiment in the construction for fixing the shoe17 in position. In the case of the first embodiment, as the finger screw18 is rotated in the tightening direction, the mount portion 172 of theshoe 17 may be pressed against the guide member 174, so that the mountportion 172 of the shoe 17 may be fixed in position relative to theguide member 174 by the finger screw 18. In this way, the shoe 17 can befixed in position relative to the tool main body 11. In contrast, in thesecond embodiment, the shoe 17 can be fixed in position relative to thetool main body 11 by using a one-touch fixing mechanism 90. Theone-touch fixing mechanism 90 is configured to be able to fix the shoe17 relative to the front housing 31 by a one touch action (i.e., asingle operation) of the operator.

The electric tool 10A of the second embodiment is different from theelectric tool 10 of the first embodiment in that the finger screw 18 andits related construction are replaced with the one-touch fixingmechanism 90. In other respect, the construction of the electric tool10A may be the same as the electric tool 10. Therefore, in FIGS. 24 to29, like members are given the same reference numerals as the firstembodiment and the description of these members will not be repeated.

As shown in FIGS. 24 to 29, the one-touch fixing mechanism 90 generallyincludes a fixed guide plate 91, a fixing screw 93, an operation lever95 and a biasing spring 97. Similar to the guide member 174 of the firstembodiment, the fixed guide plate 91 is fixed to the front housing 31 bymeans of screws. The fixed guide plate 91 is positioned to surround themount portion 172 of the shoe 17 in a manner similar to the guide member174. The mount portion 172 of the shoe 17 can slide in the forward andrearward direction under the guide of the fixed guide plate 91. Thefixing screw 93 is threadably engaged with a threaded hole 92 formed inthe fixed guide plate 91. The operation lever 95 is attached to thefixing screw 93 so as to be integrated therewith. Therefore, as theoperation lever 95 is rotated, the fixing screw 93 rotates together withoperation lever 95. The biasing spring 97 is interposed between theoperation lever 95 and the fixed guide plate 91 to normally bias theoperation lever 95 in a releasing direction to rotate the fixing screw93 in a loosening direction. As the fixing screw 93 rotates in theloosening direction, the fixing screw 93 moves away from the mountportion 172.

When the operator rotates the operation lever 95 in a fixing directionto rotate the fixing screw 93 in a tightening direction opposite to theloosening direction, the fixing screw 93 moves toward the mount portion172, so that a pressing end 94 of the fixing screw 93 protrudes inwardlyfrom the threaded hole 92 as shown in FIGS. 24 to 26. Then, the pressingend 94 of the fixing screw 93 may be pressed against the outer surfaceof the mount portion 172, so that the mount portion 172 may be fixed inposition relative to the fixed guide plate 91. In this way, theone-touch fixing mechanism 90 can fix the shoe 17 in position relativeto the tool man body 11 by the one-touch operation (single operation) ofthe operation lever 95.

On the other hand, when the operator operates the operation lever 95 torotate the same in the releasing direction that is the same direction asthe biasing direction of the biasing spring 97, the operation lever 95may rotate in the releasing direction while receiving the biasing forceof the biasing spring 97 in the same direction, so that the fixing screw93 rotates in the loosening direction relative to the threaded hole 92.Therefore, the pressing end 94 of the fixing screw 93 moves away fromthe mount portion 172 of the shoe 17. Hence, the mount portion 172 ofthe shoe 17 may be released from fixation relative to the fixed guideplate 91 and can be moved in the forward and rearward direction relativeto the front housing 31. In this way, with the one-touch fixingmechanism 90, the operation for releasing fixation of the shoe 17 can bemade by the one-touch operation (single operation) of the operationlever 95.

With the electric tool 10A according to the second embodiment, the shoe17 movable relative to the tool man body 11 (front housing 31) can befixed in position relative to the tool main body 11 (front housing 31)by the one-touch operation of the one-touch fixing mechanism 90.Therefore, after adjustment of the position of the shoe 17, the shoe 17can be fixed in position by the one-touch operation. Hence, the positionfixing operation of the shoe 17 can be easily performed. The electrictool 10A is improved in the operability in this respect.

<Third Embodiment>

A third embodiment will now be described with reference to FIGS. 30 to35. FIG. 30 shows an electric tool 10B according to the thirdembodiment. The electric tool 10B is different from the electric tool10A of the second embodiment in that the one-touch fixing mechanism 90is replaced with a one-touch fixing mechanism 90A that utilizes a togglemechanism. Thus, the electric tool 10B includes the one-tough fixingmechanism 90A that utilizes a toggle mechanism for fixing the shoe 17 inposition relative to the tool main body 11. Therefore, the one-touchfixing mechanism 90A serves as a shoe fixing device. Also, the one-touchfixing mechanism 90A is configured to be able to fix the shoe 17 by theone-touch operation (single operation) of the operator.

The electric tool 10B of the third embodiment may be the same as theelectric tool 10A of the second embodiment except for the replacement ofthe one-touch fixing mechanism 90 with the one-touch fixing mechanism90A. Therefore, in FIGS. 30 to 35, like members are given the samereference numerals as the first and second embodiments and thedescription of these members will not be repeated.

Referring to FIGS. 30 to 35, the one-touch fixing mechanism 90Agenerally includes a fixed guide plate 91A, a fastening clamp 93A, aclamp retainer 95A and a toggle operation lever 97A.

The fixed guide plate 91A may be configured to be the same as the fixedguide plate 91 of the second embodiment and may be fixed to the fronthousing 31 by means of screws. The fixed guide plate 91A also may bepositioned to surround the mount portion 172 of the shoe 17. Also, themount portion 172 of the shoe 17 can slide in the forward and rearwarddirection under the guide of the fixed guide plate 91A. A roller guideplate 92A is attached to the outer side of the fixed guide plate 91A. Atoggle roller 99A that will be explained later can roll on the rollerguide plate 92A. The fastening clamp 93A has a substantially bar-likeshape. One end (the outer end or the lower end in FIG. 32) of thefastening clamp 93A is held by the clamp retainer 95A, and the other end(inner end or the upper end in FIG. 32) of the fastening clamp 93A maycontact the inner surface of the mount portion 172. An enlarged engagingflange 94A is formed on the inner end of the fastening clamp 93A. Inthis connection, a slot having a width smaller than the engaging flange94A and larger than the clamp retainer 95A is formed in the mountportion 172. The fastening clamp 93A may be inserted into the slotformed in the mount portion 172 from the upper side as viewed in FIG.32, so that the enlarged engaging flange 94A may contact the innersurface of the mount portion 172 around the slot. Therefore, when thefastening clamp 93A moves outward (rightward), the fastening clamp 93Amay pull the mount portion 172 outward (rightward). The outer end of thefastening clamp 93A threadably engages a nut 96A that is held by theclamp retainer 95A. In this way, the outer end of the fastening clamp93A may be held by the clamp retainer 95A. A support shaft 98A issupported on the rear portion of the clamp retainer 95A. The supportshaft 98A pivotally supports the toggle operation lever 97A. Inaddition, the toggle roller 99A is supported on the clamp retainer 95Aat a position on the left side of the pivotal shaft 98A. As the toggleoperation lever 97A is operated, the toggle roller 99A may roll on theroller guide plate 92A, so that the toggle roller 99A can change itsposition. Depending on the distance between the toggle roller 99A andthe support shaft 98A, the fastening clamp 93A may be forced to moveoutward or may not be forced to move outward.

More specifically, as the toggle operation lever 97A is pushed inward(leftward) from the position shown in FIG. 35, the toggle roller 99Arolls on the roller guide plate 92A so as to move forward, so that thedistance between the toggle roller 99A and the support shaft 98Ameasured along the left and right direction may increase. Therefore, thefastening clamp 93A is pulled outward (rightward). Then, the engagingflange 94A provided on the inner end (left end) of the fastening clamp93A is forced to be pressed against the mount portion 172 of the shoe17, so that the mount portion 172 of the shoe 17 may be pressed againstthe fixed guide plate 91A as shown in FIG. 32. In this way, the shoe 17can be fixed in position relative to the fixed guide plate 91A andeventually relative to the tool main body 11. As a result, with theone-touch fixing mechanism 90A, the shoe 17 can be fixed in position bythe one-touch operation (single operation) of the toggle operation lever97A after the position of the shoe 17 relative to the tool main body 11has been adjusted or determined.

On the other hand, as the toggle operation lever 97A is pulled outward(rightward) from the position shown in FIG. 32, the toggle roller 99Arolls on the roller guide plate 92A so as to move rearward, so that thedistance between the toggle roller 99A and the support shaft 98Ameasured along the left and right direction may decrease. Therefore, theengaging flange 94A provided on the inner end (left end) of thefastening clamp 93A may not be pressed against the mount portion 172 ofthe shoe 17, so that the mount portion 172 of the shoe 172 may not bepressed against the fixed guide plate 91A as shown in FIG. 35. In thisway, the fixation of the mount portion 172 of the shoe 17 against thefixed guide plate 91A may be released. Therefore, the shoe 17 may befree to move in the forward and rearward direction. As a result, withthe one-touch fixing mechanism 90A, the fixation of the shoe 17 can bereleased by the one-touch operation (single operation) of the toggleoperation lever 97A.

Thus, also with the electric tool 10B according to the third embodiment,the shoe 17 movable relative to the tool man body 11 (front housing 31)can be fixed in position relative to the tool main body 11 (fronthousing 31) by the one-touch operation of the one-touch fixing mechanism90A. Therefore, after adjustment of the position of the shoe 17, theshoe 17 can be fixed in position by the one-touch operation. Hence, theposition fixing operation of the shoe 17 can be easily performed. Theelectric tool 10B is improved in the operability in this respect.

<Other Possible Modifications>

The above embodiments may be modified in various ways. For example,although the electric tools of the above embodiments have beenconfigured as those called dust-proof board trimmers or cut-out tools,the above teachings may be also applied to any other electric tools aslong as they have bit mounting mechanisms.

Further, the shoe 17 and the shoe fixing devices (the finger screw 18and the one-touch fixing mechanisms 90 and 90A) may not be limited tothose described above and may have any other configurations than thosedescried in the embodiments.

Further, in the above embodiments, the air is discharged to the out sidefrom the front blow opening 188 and also from the four air-blow openings36 disposed at the front portion of the tool man body 11. However, theabove embodiments may be modified not to include the four air-blowopenings 36. In this case, the electric tool has only the front blowopening 188.

What is claimed is:
 1. An electric tool configured to actuate an end tool, the electric tool comprising: a motor configured to generate a rotational drive force; an output shaft rotatably driven by the rotational drive force of the motor and having a longitudinal axis; a fan configured to rotate with the output shaft around the longitudinal axis in order to produce a cooling air flow; a support housing configured to support and house the output shaft, the motor and the fan; a controller configured to control an operation of the motor, the controller disposed within the support housing; a tool holder disposed at a front portion of the output shaft and configured to hold the end tool; an adjustment base disposed on a front side of a front end of the output shaft and capable of adjusting a machining range of the end tool; an air flow passage defined in the support housing, so that air flows in an axial direction along the longitudinal axis; wherein: the controller and motor are oriented on one side of the fan, and the tool holder and adjustment base are oriented on an opposite side of the fan; the air flow passage comprises: a suction air flow passage providing suction air by the fan, defined by a path between an inlet opening formed in the support housing and the fan, and a discharge air flow passage providing discharge air by the fan, defined between the fan and a discharge opening along the longitudinal axis; the controller and the motor are disposed in the suction air flow passage; and at least a part of the discharge air produced by the fan is discharged from the discharge opening of the discharge air flow passage axially along the longitudinal axis and directed at the adjustment base.
 2. The electric tool according to claim 1, wherein: the discharge opening is formed in the support housing and comprises a first discharge opening and a second discharge opening; the electric tool further comprises a shaft lock mechanism configured to lock the output shaft for preventing rotation of the output shaft in the rotational direction; the first discharge opening and the second discharge opening are located at different positions from each other in a front-to-rear direction along the axial direction; and the shaft lock mechanism is located between the first discharge opening and the second discharge opening in the front-to-rear direction.
 3. The electric tool according to claim 1, wherein: the discharge opening is formed in the support housing and comprises a first discharge opening and a second discharge opening; the first discharge opening and the second discharge opening are located at different positions from each other in a front-to-rear direction along the axial direction; the adjustment base comprises a mount portion mounted to and supported by the support housing; and the mount portion is located between the first discharge opening and the second discharge opening in the front-to-rear direction.
 4. The electric tool according to claim 1, wherein: a second part of the discharge air flows directly by an outer circumference of the tool holder.
 5. The electric tool according to claim 1, wherein: the discharge opening is formed in the support housing and comprises a first discharge opening and a second discharge opening; and the second discharge opening is configured to discharge air that flows directly by an outer circumference of the tool holder.
 6. The electric tool according to claim 1, wherein the tool holder is disposed in the discharge air flow passage.
 7. The electric tool according to claim 1, further comprising a rechargeable battery configured to be detachably mounted to the support housing.
 8. The electric tool according to claim 7, wherein the rechargeable battery is further configured to be mounted to and detached from the support housing as it is slid along the support housing in a direction perpendicular to the longitudinal axis.
 9. The electric tool according to claim 1, wherein: a second part of the discharge air flows directly by an outer circumference of the tool holder and/or directly through an inside of the tool holder.
 10. The electric tool according to claim 1, wherein: the discharge opening is formed in the support housing and comprises a first discharge opening and a second discharge opening; and the second discharge opening is configured to discharge air that flows directly by an outer circumference of the tool holder and/or directly through an inside of the tool holder. 